1. Field of the Invention
This invention relates to a stabilizer for a rigid chlorinated resin comprising a hydrotalcite compound and an inorganic copper compound and a rigid chlorinated resin composition whose weatherability, chalking resistance and physical properties are improved by adding said stabilizer to a rigid chlorinated resin.
2. Description of the Prior Art
In general, a chlorinated resin, which is less stable to heat and light, would frequently undergo thermal decomposition mainly caused by dehydrochlorination in a thermal molding step. As a result, the mechanical properties and the color tone of the obtained processed product are deteriorated, which brings about a serious disadvantage.
In order to avoid these problems, therefore, attempts have been made to add one or more stabilizers to chlorinated resins to thereby stabilize the same.
Among these stabilizers, lead stabilizers, which are relatively effective in imparting heat ability, are widely employed. However a chlorinated resin comprising lead stabilizers suffers from some disadvantages such that it suffers from chloration during processing and that it has a poor weatherability and thus shows chalking (i.e., whitening), in particular, when used outdoor. Thus it has been required to overcome these disadvantages.
Recently, furthermore, a higher heat stability under severe temperature conditions has been required.
In order to satisfy these requirements, Japanese Patent Laid-Open No. 150/1982 has proposed to use a lead stabilizer together with an organotin compound. However this combined use is scarcely effective on the prevention of chalking and, further, gives only a limited heat stability. Furthermore, it has been suggested to use a lead stabilizer together with a 2,6-dimethyl-1,4-dihydropyridine compound (Japanese Patent Laid-Open No. 16313/1981) or a compound having a 2,2,6,6-tetramethylpiperidine group (Japanese Patent Laid-Open No. 196351/1984). However none of these methods can give a satisfactory effect. Thus it has been required to establish an improved method.
On the other hand, a composition simultaneously containing a metal stearate would suffer from chalking. In the case of a molded product of a lead-free composition containing a large amount of various metal soaps as a stabilizer and a lubricant. In particular, serious chalking is observed. In order to prevent the chalking, Japanese Patent Laid-Open No. 57844/1981 has proposed to use a polyol partial ester. However the effect thus achieved is yet insufficient.
Furthermore, Japanese Patent Laid-Open No. 02942/1984 has proposed to use an inorganic copper compound such as cuprous chloride, cuptic chloride, copper sulfate, basic copper carbonate or copper carbonate. Although this method is effective in improving the chalking of a chlorinated resin, the heat stability, thermal coloring properties and weatherability of the chlorinated resin are deteriorated thereby.
Furthermore, an organotin compound would relatively suppress the occurrence of chalking. However, an organotin compound, in particular, an organotin mercaptide compound would deteriorate the weatherability of a chlorinated resin, which restricts the application range thereof. Thus it has been required to overcome this problem.